I've taken clones from unsexed plants, put them in a bubble cloner, then set the lights to 12/12 right away. From my experience, the clone will root first, then show sex. It's a great way to know the sex of a plant before you are done vegging it. Thus if it's a male, you can just choppy chop!
I especially do this when my box is getting crowded and growing from seed. And you don't have to wait till they are completely mature. If you had room, you could reveg the females to fill the rest of the space in your box.
Choader